CVE-2026-68164

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: disallow overlapping input ranges for damon_set_regions()

damon_set_regions() assumes the input ranges are sorted by the address and

don't overlap each other. Hence the assumption was initially to be

explicitly validated. But commit 97d482f4592f ("mm/damon/sysfs: reuse

damon_set_regions() for regions setting") has mistakenly removed the

validation.

This can make DAMON behave in unexpected ways. At the best, the

monitoring results snapshot will just look weird since there will be

overlapping regions. DAMOS will also work weirdly, applying the same

action multiple times for overlapping regions, and make DAMOS quota weird.

More seriously, depending on the setup and regions updates sequence,

negative size regions can be made. It will trigger WARN_ONCE() if the

kernel is built with CONFIG_DAMON_DEBUG_SANITY=y. Depending on the

monitoring results, the negative size region can further trigger division

by zero in damon_merge_two_regions().

Note that some of the consequences including the WARN_ONCE() and the

divide by zero depend on commits that were introduced after the root cause

commit 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for

regions setting").

Fix the problems by checking the assumption and returning an error if

the input ranges don't meet the assumption.

The issue was discovered [1] by Sashiko.